When gametes from two different species are able to fuse to form a zygote, it may have different chromosome sets, causing it to fail to undergo mitosis properly. this is an example of .

The given blank can be filled with zygotic mortality.  

Explanation:

An array of mechanisms, physiological procedures, and behaviors, which inhibit two distinct species that mate from generating offspring, or which makes sure that any produced offspring is not fertile. It can be either prezygotic, that is, obstructions that inhibit fertilization or postzygotic, that is, the obstructions, which take place after the formation of zygote.  

A kind of obstruction known as the zygotic mortality in which the sperm and egg come into contact with each other and fuse, however, the zygote dies due to the absence of further development. It is one of the forms of post-zygotic barriers.  

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